Martí Aldea - Academia.edu (original) (raw)

Papers by Martí Aldea

Biochemical Society Transactions, 1996

Molecular and cellular biology, 2009

The regulation of mRNA transport is a fundamental process for cytoplasmic sorting of transcripts ... more The regulation of mRNA transport is a fundamental process for cytoplasmic sorting of transcripts and spatially controlled translational derepression once properly localized. There is growing evidence that translation is locally modulated as a result of specific synaptic inputs. However, the underlying molecular mechanisms that regulate this translational process are just emerging. We show that KIS, a serine/threonine kinase functionally related to microtubule dynamics and axon development, interacts with three proteins found in RNA granules: KIF3A, NonO, and eEF1A. KIS localizes to RNA granules and colocalizes with the KIF3A kinesin and the beta-actin mRNA in cultured cortical neurons. In addition, KIS is found associated with KIF3A and 10 RNP-transported mRNAs in brain extracts. The results of knockdown experiments indicate that KIS is required for normal neurite outgrowth. More important, the kinase activity of KIS stimulates 3' untranslated region-dependent local translation ...

Molecular and cellular biology, 1999

Yeast cells overexpressing the Ser/Thr protein phosphatase Ppz1 display a slow-growth phenotype. ... more Yeast cells overexpressing the Ser/Thr protein phosphatase Ppz1 display a slow-growth phenotype. These cells recover slowly from alpha-factor or nutrient depletion-induced G1 arrest, showing a considerable delay in bud emergence as well as in the expression of the G1 cyclins Cln2 and Clb5. Therefore, an excess of the Ppz1 phosphatase interferes with the normal transition from G1 to S phase. The growth defect is rescued by overexpression of the HAL3/SIS2 gene, encoding a negative regulator of Ppz1. High-copy-number expression of HAL3/SIS2 has been reported to improve cell growth and to increase expression of G1 cyclins in sit4 phosphatase mutants. We show here that the described effects of HAL3/SIS2 on sit4 mutants are fully mediated by the Ppz1 phosphatase. The growth defect caused by overexpression of PPZ1 is intensified in strains with low G1 cyclin levels (such as bck2Delta or cln3Delta mutants), whereas mutation of PPZ1 rescues the synthetic lethal phenotype of sit4 cln3 mutants...

Yeast, 1997

A set of Saccharomyces cerevisiae expression vectors has been developed in which transcription is... more A set of Saccharomyces cerevisiae expression vectors has been developed in which transcription is driven by a hybrid tetO-CYC1 promoter through the action of a tetR-VP16 (tTA) activator. Expression from the promoter is regulated by tetracycline or derivatives. Various modalities of promoter and activator are used in order to achieve different levels of maximal expression. In the presence of antibiotic in the growth medium at concentrations that do not affect cell growth, expression from the tetO promoter is negligible, and upon antibiotic removal induction ratios of up to 1000-fold are observed with a lacZ reporter system. With the strongest system, overexpression levels comparable with those observed with GAL1-driven promoters are reached. For each particular promoter/tTA combination, expression can be modulated by changing the tetracycline concentration in the growth medium. These vectors may be useful for the study of the function of essential genes in yeast, as well as for phenotypic analysis of genes in overexpression conditions, without restrictions imposed by growth medium composition.

Yeast, 1998

A promoter-substitution cassette has been constructed that allows one-step substitution of chromo... more A promoter-substitution cassette has been constructed that allows one-step substitution of chromosomal gene promoters for the tetracycline-regulatable tetO promoter in yeast cells, which uses kanMX4 as selective marker for geneticin resistance. Oligonucleotides for PCR amplification of the cassette are designed to allow homologous recombination through short flanking regions of homology with the upstream sequences of the chromosomal gene, upon transformation of target cells. By testing three essential genes of chromosome XV (YOL135c, YOL142w and YOL144w), the system causes tetracycline-dependent conditional growth of the cells, being modulatable by intermediate concentrations of the effector. Analysis of terminal phenotypes of the promoter-substituted cells in the presence of the antibiotic may facilitate functional analysis of essential orphan genes.

The EMBO Journal, 2004

The G1 cyclin Cln3 is a key activator of cell-cycle entry in budding yeast. Here we show that Whi... more The G1 cyclin Cln3 is a key activator of cell-cycle entry in budding yeast. Here we show that Whi3, a negative G1 regulator of Cln3, interacts in vivo with the cyclin-dependent kinase Cdc28 and regulates its localization in the cell. Efficient interaction with Cdc28 depends on an N-terminal domain of Whi3 that is also required for cytoplasmic localization of Cdc28, and for proper regulation of G1 length and filamentous growth. On the other hand, nuclear accumulation of Cdc28 requires the nuclear localization signal of Cln3, which is also found in Whi3 complexes. Both Cln3 and Cdc28 are mainly cytoplasmic during early G1, and become nuclear in late G1. However, Whi3-deficient cells show a distinct nuclear accumulation of Cln3 and Cdc28 already in early G1. We propose that Whi3 constitutes a cytoplasmic retention device for Cln3-Cdc28 complexes, thus defining a key G1 event in yeast cells.

Oncogene, 2011

Alterations in the levels of adhesion and motility of cells are critical events in the developmen... more Alterations in the levels of adhesion and motility of cells are critical events in the development of metastasis. Cyclin D1 (CycD1) is one of the most frequently amplified oncogenes in many types of cancers and it is also associated with the development of metastasis. Despite this, we still do not know which are all the relevant pathways by which CycD1 induces oncogenic processes. CycD1 functions can be either dependent or independent of the cyclin-dependent kinase Cdk4, and they affect several cellular aspects such as proliferation, cell attachment and migration. In this work, we reveal a novel function of CycD1 that fosters our understanding of the oncogenic potential of CycD1. We show that CycD1 binds to the small GTPases Ral A and B, which are involved, through exocyst regulation, in the progression of metastatic cancers, inducing anchorage-independent growth and cell survival of transformed cells. We show that CycD1 binds active Ral complexes and the exocyst protein Sec6, and co-localizes with Ral GTPases in trans-Golgi and exocyst-rich regions. We have also observed that CycD1-Cdk4 phosphorylates the Ral GEF Rgl2 'in vitro' and that CycD1-Cdk4 activity stimulates accumulation of the Ral GTP active forms. In accordance with this, our data suggest that CycD1-Cdk4 enhances cell detachment and motility in collaboration with Ral GTPases. This new function may help explain the contribution of CycD1 to tumor spreading.

Nature Communications, 2012

Budding yeast cells are assumed to trigger Start and enter the cell cycle only after they attain ... more Budding yeast cells are assumed to trigger Start and enter the cell cycle only after they attain a critical size set by external conditions. However, arguing against deterministic models of cell size control, cell volume at Start displays great individual variability even under constant conditions. Here we show that cell size at Start is robustly set at a single-cell level by the volume growth rate in G1, which explains the observed variability. We find that this growth-rate-dependent sizer is intimately hardwired into the Start network and the Ydj1 chaperone is key for setting cell size as a function of the individual growth rate. Mathematical modelling and experimental data indicate that a growth-rate-dependent sizer is sufficient to ensure size homeostasis and, as a remarkable advantage over a rigid sizer mechanism, it reduces noise in G1 length and provides an immediate solution for size adaptation to external conditions at a population level.

Molecular Microbiology, 2001

Moderate hyperosmotic stress on Saccharomyces cerevisiae cells produces a temporary delay at the ... more Moderate hyperosmotic stress on Saccharomyces cerevisiae cells produces a temporary delay at the G 1 stage of the cell cycle. This is accompanied by transitory downregulation of CLN1, CLN2 and CLB5 transcript levels, although not of CLN3, which codes for the most upstream activator of the G 1 /S transition. Osmotic shock to cells synchronized in early G 1 , when Cln3 is the only cyclin present, causes a delay in cell cycle resumption. This points to Cln3 as being a key cell cycle target for osmotic stress. We have observed that osmotic shock causes downregulation of the kinase activity of Cln3±Cdc28 complexes. This is concomitant with a temporary accumulation of Cln3 protein as a result of increased stability. The effects of the osmotic stress in G 1 are not suppressed in CLN3-1 cells with increased kinase activity, as the Cln3±Cdc28 activity in this mutant is still affected by the shock. Although Hog1 is not required for the observed cell cycle arrest in hyperosmotic conditions, it is necessary to resume the cell cycle at KCl concentrations higher than 0.4 M.

Molecular Cell, 2007

G1 cyclin Cln3 plays a key role in linking cell growth and proliferation in budding yeast. It is ... more G1 cyclin Cln3 plays a key role in linking cell growth and proliferation in budding yeast. It is generally assumed that Cln3, which is present throughout G1, accumulates passively in the nucleus until a threshold is reached to trigger cell cycle entry. We show here that Cln3 is retained bound to the ER in early G1 cells. ER retention requires binding of Cln3 to the cyclindependent kinase Cdc28, a fraction of which also associates to the ER. Cln3 contains a chaperone-regulatory J i domain that counteracts Ydj1, a J chaperone essential for ER release and nuclear accumulation of Cln3 in late G1. Finally, Ydj1 is limiting for release of Cln3 and timely entry into the cell cycle. As protein synthesis and ribosome assembly rates compromise chaperone availability, we hypothesize that Ydj1 transmits growth capacity information to the cell cycle for setting efficient size/ ploidy ratios.

Molecular and Cellular Biology, 2003

The transcriptional activator Ime1 is a key regulator of meiosis and sporulation in budding yeast... more The transcriptional activator Ime1 is a key regulator of meiosis and sporulation in budding yeast. Ime1 is controlled at different levels by nutrients and cell-type signals. Previously, we have proposed that G 1 cyclins would transmit nutritional signals to the Ime1 pathway by preventing the accumulation of Ime1 within the nucleus. We show here that nutritional signals regulate the subcellular localization of Ime1 through the TOR pathway. The inactivation of TOR with rapamycin promotes the nuclear accumulation and stabilization of Ime1, with consequent induction of early meiotic genes. On the contrary, the activation of TOR by glutamine induces the relocalization of Ime1 to the cytoplasm. Thus, TOR may sense optimal nitrogen-and carbonlimiting conditions to modulate Ime1 function. Besides TOR, ammonia induces an independent mechanism that prevents the accumulation of Ime1 in the nucleus. Both TOR and ammonia regulate Ime1 localization in the absence of Cdk1 activity and therefore use mechanisms different from those exerted by G 1 cyclins. Integration of independent mechanisms into a single early controlling step, such as the nuclear accumulation of Ime1, may help explain why yeast cells execute the meiotic program only when the appropriate internal and external conditions are met together.

Nucleic Acids Research, 1998

We have developed an activator/repressor expression system for budding yeast in which tetracyclin... more We have developed an activator/repressor expression system for budding yeast in which tetracyclines control in opposite ways the ability of tetR-based activator and repressor molecules to bind tetO promoters. This combination allows tight expression of tetO-driven genes, both in a direct (tetracycline-repressible) and reverse (tetracycline-inducible) dual system. Ssn6 and Tup1, that are components of a general repressor complex in yeast,